<template>
  <div class="pagination">
    <button :disabled="pageNo <= 1" @click="$emit('changePageNo', pageNo - 1)">
      上一页
    </button>
    <button
      v-show="continueStartEnd.start > 1"
      @click="$emit('changePageNo', 1)"
    >
      1
    </button>

    <button v-show="continueStartEnd.start > 2">···</button>

    <button
      :class="{ active: page === pageNo }"
      @click="$emit('changePageNo', page)"
      v-for="page in continuePagesArr"
      :key="page"
    >
      {{ page }}
    </button>

    <button v-show="continueStartEnd.end < totalPages - 1">···</button>
    <button
      @click="$emit('changePageNo', totalPages)"
      v-show="continueStartEnd.end < totalPages"
    >
      {{ totalPages }}
    </button>
    <button
      :disabled="pageNo === totalPages"
      @click="$emit('changePageNo', pageNo + 1)"
    >
      下一页
    </button>
  </div>
</template>

<script>
export default {
  name: "Pagination",
  props: ["pageNo", "totalPages", "continuePage"],
  computed: {
    continueStartEnd() {
      const { pageNo, totalPages, continuePage } = this;
      // 起始页和结尾页
      let start = 0;
      let end = 0;

      start = pageNo - Math.floor(continuePage / 2);
      end = pageNo + Math.floor(continuePage / 2);

      if (start < 1) {
        start = 1;
        end = continuePage;
      }

      if (end > totalPages) {
        end = totalPages;
        start = totalPages - continuePage + 1;
      }
      // console.log(start, end);
      return { start, end };
    },
    //   解决v-for v-if 冲突问题
    continuePagesArr() {
      const { start, end } = this.continueStartEnd;
      let arr = [];
      for (let i = 1; i <= end; i++) {
        if (i >= start) {
          arr.push(i);
        }
      }
      return arr;
    }
  }
};
</script>

<style lang="less" scoped>
.pagination {
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
</style>
